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Chapter 2. Spring Integration

2.1. Integration with Drools Expert
2.1.1. Define a Resource
2.1.2. Event Listeners

2.1. Integration with Drools Expert

In this section we will explain the drools namespace.

Execution nodes are a context to regsiter ksessions and kbases against for lookup.

Table 2.1. 

AttributeDescriptionRequired
idBean's id is the name to be reference from other beans.Yes

Table 2.2. 

AttributeDescriptionRequired
idBean's id is the name to be reference from other beans.Yes, but can be omitted when this tag is nested.
sourceThe path to the file containing the actual resource.Yes
typeType of the Resource as is defined in class ResourceType.No, default to DRL

When configuring a decision table resource you can nest a <drools:decisiontable-conf> tag to configure the resource.

Table 2.3. 

AttributeDescriptionRequired
input-typeDecision Table input type: XLS or CSVNo
worksheet-nameThe worksheet name to be used in the when using an XLSNo

Example 2.1. resource definition example


<drools:resource source="classpath:org/drools/IntegrationExampleTest.xls"

                 type="DTABLE">

   <drools:decisiontable-conf input-type="XLS" worksheet-name="Tables_2" />

</drools:resource>

Table 2.4. 

AttributeDescriptionRequired
idBean's id is the name to be referenced from other beans.Yes
nodeExecution-Node context to register the kbase withno

A Knowledge Base has a 0..n resources. Has two nested elements, resources and configuratoins. Thoe resources can be inner elements or references, using the "ref" attribute.

Example 2.2. kbase definition example


<drools:kbase id="kbase1" node="node1">

   <drools:resources> 

      <drools:resource source="classpath:org/drools/spring/IntegrationExampleTest.xls" 

                    type="DTABLE">

         <drools:decisiontable-conf input-type="XLS" worksheet-name="Table_2" />

      </drools:resource>



      <drools:resource ref="resource1"/>



      <drools:resource source="classpath:org/drools/container/spring/model.xsd" />

   </drools:resources>



   <drools:configuration>

       <drools:mbeans enabled="true" />



      <drools:accumulate-functions>

         <drools:accumulate-function name="func1" ref="func1Instance" />

         <drools:accumulate-function name="func1" ref="func2Instance" />

      </drools:accumulate-functions>

   </drools:configuration>



</drools:kbase>

  • advanced-process-rule-integration

    • enabled = true : false

  • multithread

    • enabled = true : false

    • max-threads = 1..n

  • mbeans

    • enabled = true : false

  • event-processing-mode

    • mode = STREAM : CLOUD

  • accumulate-functions

    • accumulate-function 0..n

      • name = String

      • ref = String

  • evaluators

    • evaluator 0..n

      • name = String

      • ref = String

  • assert-behavior

    • mode = IDENTITY : EQUALITY

Figure 2.1. Knowledge Base Configuration Options


Table 2.5. 

AttributeDescriptionRequired
idBean's id is the name to be referenced from other beans.Yes
typeis the session stateful or stateless?Yes
name No; defaults to id when omitted.
nodeExecution-Node context to register the ksession withno
listenersSpecifies the reference to the event listeners group (see 'Defining a Group of listeners' section below).no

Example 2.3. ksession definition example


<drools:ksession id="ksession1" type="stateless" 

                  name="stateless1" kbase="kbase1"/>



<drools:ksession id="ksession2" type="stateful" kbase="kbase1"/>



<drools:ksession id="ksession3" type="stateful" kbase="kbase2>



   <drools:batch>

      <drools:insert-object ref="person" />



      <drools:set-global identifier="list1">

          <bean class="java.util.ArrayList" />

      </drools:set-global>



      <drools:startProcess process-id="start fire"> 



   </drools:batch>



   <drools:configurations>

     <drools:keep-reference enabled="false" />

     <drools:clock-type type="PSEUDO"  />

   </drools:configurations>



</drools:ksession>

  • keep-reference

    • enabled = true : false

  • clock-type

    • type = REALTIME : PSEUDO

  • jpa-persistence

    • transaction-manager

      • ref = String

    • entity-manager-factory

      • ref = String

    • variable-persisters

      • for-class = String

      • implementation = String

Figure 2.2. Knowledge Session Configuration Options


  • insert-object

    • ref = String (optional)

    • Anonymous bean

  • set-global

    • identifier = String (required)

    • reg = String (optiona)

    • Anonymous bean

  • fire-all-rules

    • max : n

  • fire-until-halt

  • start-process

    • parameter

      • identifier = String (required)

      • ref = String (optional)

      • Anonymous bean

  • signal-event

    • ref = String (optional)

    • event-type = String (required)

    • process-instance-id =n (optional)

Figure 2.3. Initialization Batch Commands


Example 2.4. ksession JPA configuraiton example


<drools:kstore id="kstore" /> <!-- provides KnowledgeStoreService implementation -->



<bean id="myEmf" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">

   <property name="dataSource" ref="ds" />

   <property name="persistenceUnitName" value="org.drools.persistence.jpa.local" />

</bean>



<bean id="txManager" class="org.springframework.orm.jpa.JpaTransactionManager">

   <property name="entityManagerFactory" ref="myEmf" />

</bean>

   

<drools:ksession id="jpaSingleSessionCommandService" type="stateful"  kbase="kbProcessWorkItems">

   <drools:configuration>

      <drools:jpa-persistence>

         <drools:transaction-manager ref="txManager" />

         <drools:entity-manager-factory ref="myEmf" />   

      </drools:jpa-persistence>

   </drools:configuration>

</drools:ksession>

When configuring a Event Listener resource you can nest a <drools:eventListener> tag to configure the listener.

Drools supports adding 3 types of listeners to KnowledgeSessions - AgendaListener, WorkingMemoryListener, ProcessEventListener

The drools-spring module allows you to configure these listeners to KnowledgeSessions using XML tags. These tags have identical names as the actual listener interfaces i.e., <drools:agendaEventListener....>, <drools:workingMemoryEventListener....> and <drools:processEventListener....>.

drools-spring provides features to define the listeners as standalone (individual) listeners and also to define them as a group.

Table 2.6. 

AttributeRequiredDescription
refNoA reference to another declared bean.


Example 2.5. Listener configuration example - using a bean:ref.


  <drools:resource id="resource1" type="DRL" source="classpath:org/drools/container/spring/testSpring.drl"/>



  <drools:kbase id="kbase1">

    <drools:resources>

      <drools:resource ref="resource1"/>

    </drools:resources>

  </drools:kbase>



  <bean id="mock-agenda-listener" class="org.drools.container.spring.MockAgendaEventListener" />

  <bean id="mock-wm-listener" class="org.drools.container.spring.MockWorkingMemoryEventListener" />

  <bean id="mock-process-listener" class="org.drools.container.spring.MockProcessEventListener" />



  <drools:ksession id="statefulSession" type="stateful" kbase="kbase1" node="node1">

    <drools:agendaEventListener ref="mock-agenda-listener"/>

    <drools:processEventListener ref="mock-process-listener"/>

    <drools:workingMemoryEventListener ref="mock-wm-listener"/>

  </drools:ksession>

Example 2.6. Listener configuration example - using nested bean.


  <drools:resource id="resource1" type="DRL" source="classpath:org/drools/container/spring/testSpring.drl"/>



  <drools:kbase id="kbase1">

    <drools:resources>

      <drools:resource ref="resource1"/>

    </drools:resources>

  </drools:kbase>



  <drools:ksession id="statefulWithNestedBean" type="stateful" kbase="kbase1" node="node1">



    <drools:agendaEventListener>

      <bean class="org.drools.container.spring.MockAgendaEventListener"/>

    </drools:agendaEventListener>



    <drools:workingMemoryEventListener>

      <bean class="org.drools.container.spring.MockWorkingMemoryEventListener"/>

    </drools:workingMemoryEventListener>



    <drools:processEventListener>

      <bean class="org.drools.container.spring.MockProcessEventListener"/>

    </drools:processEventListener>



  </drools:ksession>

When a listener is defined without a reference to a implementing bean and does not contain a nested bean, <drools:workingMemoryEventListener/> the underlying implementation adds the Debug version of the listener defined in the API.

The debug listeners print the corresponding Event toString message to System.err.

Example 2.7. Listener configuration example - defaulting to the debug versions provided by the Knowledge-API .


  <drools:resource id="resource1" type="DRL" source="classpath:org/drools/container/spring/testSpring.drl"/>



  <drools:kbase id="kbase1">

    <drools:resources>

      <drools:resource ref="resource1"/>

    </drools:resources>

  </drools:kbase>



  <drools:ksession id="statefulWithDefault" type="stateful" kbase="kbase1" node="node1">



    <drools:agendaEventListener/> <!-- attaches the org.drools.event.rule.DebugAgendaEventListener -->

    <drools:workingMemoryEventListener/> <!-- attaches the org.drools.event.rule.DebugWorkingMemoryEventListener -->

    <drools:processEventListener/> <!-- attaches the org.drools.event.DebugProcessEventListener -->



  </drools:ksession>

The drools-spring module allows you to mix and match the different declarative styles within the same KnowledgeSession. The below sample provides more clarity.

Example 2.8. Listener configuration example - mix and match of 'ref'/nested-bean/empty styles.


  <drools:resource id="resource1" type="DRL" source="classpath:org/drools/container/spring/testSpring.drl"/>



  <drools:kbase id="kbase1">

    <drools:resources>

      <drools:resource ref="resource1"/>

    </drools:resources>

  </drools:kbase>



  <bean id="mock-agenda-listener" class="org.drools.container.spring.MockAgendaEventListener" />



  <drools:ksession id="statefulWithMixAndMatchOfStyles" type="stateful" kbase="kbase1" node="node1">



     <drools:workingMemoryEventListener>

      <bean class="org.drools.container.spring.MockWorkingMemoryEventListener"/>

    </drools:workingMemoryEventListener>



    <drools:agendaEventListener ref="mock-agenda-listener"/>



    <drools:processEventListener/> <!-- attaches the org.drools.event.DebugProcessEventListener -->



  </drools:ksession>

It is also valid to define multiple beans of the same event listener types for a KnowledgeSession.

Example 2.9. Listener configuration example - multiple listeners of the same type.


  <drools:resource id="resource1" type="DRL" source="classpath:org/drools/container/spring/testSpring.drl"/>



  <drools:kbase id="kbase1">

    <drools:resources>

      <drools:resource ref="resource1"/>

    </drools:resources>

  </drools:kbase>



  <bean id="mock-wm-listener" class="org.drools.container.spring.MockWorkingMemoryEventListener" />



  <drools:ksession id="statefulWithMultipleSameType" type="stateful" kbase="kbase1" node="node1">



    <!-- 2 different implementations of the same listener attached to one ksession -->

    <drools:workingMemoryEventListener>

      <bean class="org.drools.container.spring.ConsoleWorkingMemoryEventListener"/>

    </drools:workingMemoryEventListener>



    <drools:workingMemoryEventListener ref="mock-wm-listener"/>



  </drools:ksession>

drools-spring allows for grouping of listeners. This is particularly useful when you define a set of listeners and want to attach them to multiple sessions. The grouping feature is also very useful, when we define a set of listeners for 'testing' and then want to swtich them for 'production' use.

Table 2.7. 

AttributeRequiredDescription
IDyesUnique identifier

Note

The above mentioned child elements can be declared in any order. Only one declaration of each type is allowed in a group.

Example 2.10. Group of listeners - example


  <drools:resource id="resource1" type="DRL" source="classpath:org/drools/container/spring/testSpring.drl"/>



  <drools:kbase id="kbase1">

    <drools:resources>

      <drools:resource ref="resource1"/>

    </drools:resources>

  </drools:kbase>



  <bean id="mock-wm-listener" class="org.drools.container.spring.MockWorkingMemoryEventListener" />



  <drools:ksession id="statelessWithGroupedListeners" type="stateless" kbase="kbase1" node="node1" listeners="

mockListeners
"/>



  <drools:eventListeners id="mockListeners">

    <drools:agendaEventListener ref="mock-agenda-listener"/>

    <drools:processEventListener ref="mock-process-listener"/>

    <drools:workingMemoryEventListener ref="mock-wm-listener"/>

  </drools:eventListeners>



  <drools:eventListeners id="debugListeners">

    <drools:agendaEventListener/>

    <drools:processEventListener/>

    <drools:workingMemoryEventListener/>

  </drools:eventListeners>